Infirmity means a physical or mental weakness, especially one that comes with age or illness. When someone has an infirmity, their body or mind doesn't work as well as it used to. An elderly person might walk with a cane because of an infirmity in their legs, or need glasses because of an infirmity in their vision.

The word often describes ongoing weaknesses rather than temporary problems. If you catch the flu, that's an illness, not an infirmity. But if your grandmother has arthritis that makes her hands stiff and sore every day, that's an infirmity. If a veteran has a permanent injury from war, that's an infirmity.

In stories, characters might struggle with infirmities but still accomplish great things. A scientist with failing eyesight might continue groundbreaking research, or an aging athlete might coach young players even though their own body can no longer compete. The word reminds us that weakness in one area doesn't mean weakness everywhere. Someone can have physical infirmities but still possess great wisdom, courage, or skill.

The related adjective infirm describes someone weakened by age or illness. You might read about an infirm king who can no longer ride into battle but still rule wisely from his throne.